1. Field of the Invention
The present invention relates to electrical fans, and particularly to rotary fans which have bearings with good lubricating characteristics.
2. Prior Art
Many computer electronic devices such as central processing units (CPUs) generate a lot of heat during normal operation. This can deteriorate their operational stability and damage associated electronic equipment. The heat must be removed efficiently to ensure normal operation. Fans are therefore often used to facilitate cooling of the CPU. Good performance of the fans mostly depends on performance characteristics of bearings used in the fans. Good lubricating qualities of the bearings increase the life-span of the bearings.
FIG. 3 shows a conventional fan 90. The fan 90 comprises a sleeve 94, a bearing 92 secured within the sleeve 94, and a shaft 98 rotatably extending through the bearing 92. The fan 90 further comprises an oil retaining ring 96 located above the bearing 94. There is a gap between a circumferential surface of the ring 96 and an inner circumference of a top end of the sleeve 94. In operation, lubricating oil originating from the bearing 94 passes out through the gap and is lost. Lubrication of the bearing 94 gradually diminishes. This shortens the life-span of the bearing 94.
Thus a fan having a bearing with an oil-tight seal is desired.
Accordingly, an object of the present invention is to provide a fan which has a bearing with good lubrication characteristics.
To achieve the above-mentioned object, a fan in accordance with the present invention comprises a frame, a stator, an impeller, and an oil retainer. The frame comprises a sleeve having a bearing secured therein. The stator surrounds the sleeve. The impeller is attached on the frame and surrounds the stator. The impeller comprises an inner ring, and an outer ring spaced from the inner ring. The oil retainer comprises a small cylinder received in the stator, and a large cylinder received in a space between the inner and outer rings. The outer ring and large cylinder cooperatively form a seal therebetween. A sealed chamber is thus defined between the large cylinder and the impeller. A shaft is fixedly secured in the impeller, and extends through the oil retainer and the bearing. A gap is defined between the shaft and the small cylinder. In operation, lubricating oil originating from the bearing passes through the gap to the sealed chamber, and flows back to the bearing. Lubrication of the bearing is thus consistently maintained.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which: